An A/D converter includes a plurality of AD converting sections that sequentially operate at predetermined intervals. The AD converting section has an ADC that converts an analog signal into a digital signal and outputs the digital signal, a memory that stores, as a specific polarity value, the polarity of a signal obtained by the ADC digitizing an analog signal at a reference voltage, an analog polarity converting circuit that inverts the polarity of the analog signal based on the specific polarity value and a set polarity value, which is previously set, and a digital polarity converting circuit that inverts the polarity of the digital signal based on the specific polarity value and the set polarity value.